1. Technical Field
The present invention relates to a recording tape cartridge which rotatably accommodates, within a case, a reel around which a recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes for example are used as external recording media for computers and the like. There are recording tapes which can record a large amount of information. There are recording tape cartridges which rotatably accommodate a single reel on which such a recording tape is wound. Among such cartridges, there is a type which requires little space for accommodation at the time of storage thereof. The reel has a hub provided at the axially central portion thereof, and a pair of flanges which oppose one another and extend outwardly in the radial direction from both axial direction end portions of the hub or vicinities thereof. The recording tape is wound around the outer periphery of the hub between the pair of flanges.
Such a recording tape cartridge has a braking means so that the reel does not rotate within the case when the recording tape cartridge is not in use (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 63-251983). This JP-A No. 63-251983 discloses the following structure: an engaging gear is provided in an annular form at the floor surface of a reel hub which is shaped as a cylindrical tube having a floor and which structures the axially central portion of a reel. A locking member, which is disc-shaped and at which is provided a braking gear which can mesh with the engaging gear, is inserted within the reel hub. The locking member is supported so as to be unable to rotate with respect to the case, and so as to be slidable in the axial direction of the reel. Due to the urging force of a compression coil spring provided between the case and the locking member, the braking gear is made to mesh with the engaging gear of the reel. In this state, the reel is pressed against the floor plate of the case by the urging force of the compression coil spring. Rotation of the reel with respect to the case is locked due to the braking gear of the locking member meshing with the engaging gear due to this urging force.
In this structure, a through hole is formed in the floor portion of the reel hub. When a releasing portion of a drive device enters in from this through hole and pushes the locking member upward against the urging force of the compression coil spring, the meshed-together state of the braking gear and the engaging gear is cancelled, and rotation of the reel with respect to the case is permitted. The releasing portion of the drive device is provided at a rotating shaft together with a driving gear which meshes with a reel gear formed at the end surface of the reel hub. As the driving gear meshes with the reel gear, the releasing portion pushes the locking member upward. Accordingly, in this structure, when the rotating shaft drives and rotates the reel, the locking member, which cannot rotate with respect to the case, and the releasing portion, which rotates integrally with the rotating shaft, slidingly-contact one another while being pressed against one another due to the urging force of the compression coil spring. In order to reduce the resistance to rotation which arises accompanying this sliding-contact, the locking member and the releasing portion are both formed of resin materials.
Further, a structure which is similar to that disclosed in above-described JP-A No. 63-251983 has been conceived of in which a releasing member, which rotates integrally with the reel, is provided between the locking member and the floor portion of the reel hub (see, for example, Japanese Patent No. 3187022). Specifically, due to the releasing member being pushed by a releasing portion of a drive device, the releasing member is pushed upward together with the locking member against the urging force of the compression coil spring. In this way, the locking member is pushed upward by the releasing portion via the releasing member, and the locked state of the reel is cancelled. In this structure, due to the releasing member rotating integrally with the reel at the time when the reel is driven to rotate, the releasing portion and the releasing member do not slidingly-contact one another, and the releasing member and the locking member slidingly-contact one another.
Moreover, a structure is known in which, at the time when the reel is driven to rotate, the locking member does not slidingly-contact any other portion (see, for example, JP-A No. 11-25648). In this structure, the engaging gear is formed at the outer peripheral portion of a flange of the reel. Rotation of the reel is locked due to two locking members, each of which is rotatably supported within the case and is urged in a direction of meshing with the engaging gear, meshing together with the engaging gear. When this recording tape cartridge is loaded into a drive device, the locking members are pushed by releasing portions of the drive device, and rotate against the aforementioned urging force. In this way, the meshing together of the locking members and the engaging gear is released, and rotation of the reel is permitted. These releasing portions are respectively provided independently of the rotating shaft, and push the locking members due to the loading of the recording tape cartridge (the case) into the drive device or the lowering of the recording tape cartridge (the case) within the drive device. In this structure, the compression coil spring, which is for pressing the reel against the case or the rotating shaft, is connected to the reel via a bearing. Relative rotation between the compression coil spring and the reel is absorbed by the bearing.
However, in the recording tape cartridges relating to the above-described structures, when the recording tape is not being used, the reel is pressed against the floor plate of the case by the urging force of the compression coil spring, and is thereby held with respect to the case. Therefore, when force resisting the urging force of the compression coil spring is applied, upward and downward movement of the reel within the case cannot be impeded. Thus, for example, if the region where the reel gear is formed at the reel, which region is exposed from the case (i.e., the outer surface of the floor portion of the reel hub), is pushed or if impact of a drop is applied to this region, the reel joggles greatly within the case, which is a cause of damage to the recording tape whose one end portion is held at the case via a leader member. Further, if the reel joggles greatly within the case and the flanges of the reel interfere with the case, the flanges may deform and cause damage to the recording tape. Namely, changes in the posture of the reel and deformation of the reel are causes of damage to the recording tape.